—Review Paper—Current State-Of-The-Art Measurements Of Ozone In The Gas Phase And In Solution

This paper is a critical review and summary of the analytical procedures currently used by operating water utilities to control ozone treatment processes, considering disinfection as well as the many oxidative applications of ozone in water treatment applications. The role of common interferences in the various methods is described.

In operating U S., Canadian, European, and Japanese water treatment plants currently employing ozone as a primary disinfectant, ozone nearly always is followed by the addition of small quantities of chlorine, chlorine dioxide, or chloramine to provide the residual in the distribution system and to act as a secondary disinfectant. Clearly, the analytical procedures used must distinguish between the various species. This review critically presents these various factors and their implication with respect to “true values” of ozone determined under widely varying conditions.     

HT—5型碘量定硫仪的研制──通氮燃烧碘量法测定生铁和铸铁中硫

采用通氮燃烧、碘量法测定锰铁、硅铁等铁合金及生铁和铸铁中的Ｓ，可不依靠标样，直接从标液的消耗量求得Ｓ的含量，取得满意结果。设计研制了一种新型定Ｓ仪，较好地解决了ＳＯ２的转化、吸附和逸逃问题，大大提高了终点检测的稳定性。     

聚乙二醇——I_3~-作指示剂碘量法滴定铜

聚乙二醇是特殊表面活性剂 ,可作为沉淀胶体的保护剂 ,I- 3 作为吸附指示剂 ,利用I- 3与聚乙二醇相互作用生成的红褐色化合物 ,滴定至终点附近突变为肉红色 ,建立了碘量法滴定铜的新方法。该方法的准确度高 ,精密度好 ,平均回收率在 99.0 %— 10 0 .35 %。     

石灰法脱硫后石灰渣中硫含量分析

把石灰粉喷入烟气中脱硫,脱硫后石灰渣中硫绝大部分以亚硫酸钙的形式存在,同时含有硫酸钙,能准确测定石灰渣中硫含量,确定脱硫效率对工艺操作者起着指导生产的作用。有了准确的数据,能使工艺操作人员根据数据进行调整,保证二氧化硫的去除率,达到环保设施的要求。采用燃烧碘量法测定石灰渣中硫含量,能够测量0.1%~20%范围的硫含量,是现有检测方法中综合成本最低的一种方法。操作简单,完全自动化,节省成本,分析时间短、分析过程减少了许多危险因素。     

活性炭富集分离-碘量法测定金矿石中金的不确定度评定

运用不确定度的理论,对活性炭富集分离-碘量法测定金矿石中金含量的不确定度来源及其对不确定度的影响进行分析,并对引起不确定度分量进行了量化计算,建立了活性炭分离富集-碘量法测定金矿石中金的不确定度的评定和计算方法,得出了标准不确定度、扩展不确定度,并以不确定度的形式给出测试结果。     

Oxygen nonstoichiometry and electrical transport properties of Pr1-xCaxMnO3 ceramics

The defect chemistry of solid solutions formed by the two orthorhombic perovskite-type compounds CaMnO₃ and PrMnO₃ is strongly determined by mixed valence states emerging from the presence of trivalent or tetravalent Mn-cations, Mn³⁺ and Mn⁴⁺. Both, thermogravimetric analysis as well as measurements of DC-conductivity at elevated temperatures in dependence of the partial pressure of oxygen quantitatively reveal the extent of oxygen vacancy formation in highly densified ceramic pellets originally consolidated by sintering in pure oxygen O₂. Iodometry additionally serves to analyse the average valence state of Mn-cations and thus of the deficiency in oxygen after targeted thermal treatments under specific redox conditions. The determination of electrical transport properties including also the careful inspection of the Seebeck-effect for such specimens demonstrates that the mobility of electrons is drastically reduced when the number of oxygen vacancies increases. For the specific composition Pr_0.7Ca_0.3MnO₃, an oxide potentially relevant for resistively switching memory device applications, this is the case when the deficiency in oxygen exceeds a concentration of 1000 ppm. Detailed crystallographic studies based on refined neutron-diffraction experiments for reduced ceramic material suggest, that the reduction in electron transfer rates between tri- and tetravalent cations of manganese originates from an anisotropy effect: In the case of comparatively large oxygen deficiency, vacancies preferentially form on lattice sites in the equatorial plane of MnO₆-octahedra rather than on their apices.     

An Alternative Approach to Gas Phase Ozone Determination

A pragmatic, real time procedure to determine gas phase ozone concentration is presented. The procedure requires syringe extraction of an air-ozone sample via a Teflon septum followed by ozone measurement using the indigo method. The results are confirmed by comparison to the standard iodometric technique. The method has a number of potential applications, including as an alternative to continuous gas phase UV monitoring, if UV absorbing compounds other than ozone are present.     

改进碘量法测定二氧化氯纯度的研究

利用红外光谱和紫外光谱研究了化学法二氧化氯发生器所产生的二氧化氯混合消毒液的光谱性质．氯酸钠和盐酸反应体系温度的升高,有利于二氧化氯纯度的提高;混合气体通过尿素溶液进行纯化,可大大提高二氧化氯的纯度．     

Determination and Validation of Henry’s Constant for Ozone in Phosphate Buffers Using Different Analytical Methodologies

Different procedures for measuring the concentration of ozone in aqueous buffered solutions have been reviewed for the determination of Henry’s constant at different temperatures and pH. Iodometry, indigo trisulfonate and iron (II) chemical methods were compared with the direct UV absorbance measurement of ozone at 258 nm. From these data a new value for the molar extinction coefficient of ozone is proposed as 3840 ± 109 M^?1 cm^?1. After the verification of the ozone analysis methods, the solubility of ozone in phosphate buffer medium was studied with in-situ absorbance direct measurements in a device with high gas-liquid transference rate, minimizing the gas desorption process on sample manipulation. The decomposition of ozone was not detected at the experimental conditions tested and, consequently, the observed solubility of ozone is constant, with the pH ranging from 2 to 7.6. The solubility of ozone was measured between 5 and 35 °C, resulting in a dimensionless solubility ratio of H_B0 = 1.797 exp[0.0277·t(°C)].     

A sensitive spectrophotometric method for lipid hydroperoxide determination

A spectrophotometric method for the quantitation of lipid hydroperoxides is described. The chromophore produced in the reaction is the strongly absorbing I ₃ ⁻ ion, which has been used previously by many researchers. The present method deviates from earlier methods in three respects—first, the assay is done at low acid concentrations; second, the iodide concentration is reduced; and third, Fe²⁺ is used as a catalyst. As a result of these modifications the interference from oxygen is minimized. The assay is fast, sensitive and simple to perform.